It is often desirable to perform operations such as synchronization and channel estimation by using a pilot sequence signal in a mobile communication system. In a TD-SCDMA system, for example, a downlink pilot time slot (DwPTS) signal can be used for downlink synchronization and an uplink pilot time slot (UpPTS) signal can be used for uplink synchronization. After receiving a signal containing a pilot sequence signal, a receiver can detect the pilot sequence signal in the received signal with a specific detection algorithm and perform an operation such as synchronization operation dependent upon the detection result.
However, in a practical application, a pilot sequence signal may be transmitted overlapping with a service data signal at a time, that is, the pilot sequence signal and the service data signal may be arranged in the same time slot, in view of spectrum utilization and the like. For a time division system with a special frame structure, for example, a pilot sequence signal may cause cross-interference in a time slot to a service data signal due to a propagation delay or other reasons, and at this time it might be highly possible to degrade greatly the performance of detecting the pilot sequence signal without taking any measure and thus influence seriously the quality of communication. For example, an UpPTS signal may fall into a time slot TS1 where a service data signal is arranged due to a propagation delay under the condition of wide coverage in a TD-SCDMA system. Moreover in a special scenario, for example, in order to avoid interference of a DwPTS signal from a remote base station with the reception of an UpPTS signal at the local base station, it may also be possible to displace the UpPTS signal directly into a time slot where a service data signal is arranged and transmit the overlapping signals, and at this time the UpPTS signal might be interfered seriously by the service data signal in the time slot without taking any measure.
Transmission of a service data signal and a pilot sequence signal overlapping with each other may make it rather difficult to detect either of the service data signal or the pilot sequence signal. In the prior art, the transmission of the service data signal and the pilot sequence signal overlapping with each other is prevented as could as possible, for example, by transmitting them in separate time slots with a guard interval in a time division system. If it is impractical to avoid transmission of the overlapping service data signal and pilot sequence signal, an approach to deal with this in the prior art is to guarantee the performance of detecting the respective pilot sequence signal and service data signal with a reasonable limitation of transmission power. In a TD-SCDMA system, for example, in order to avoid strong interference of a DwPTS signal from a remote base station with the reception of an UpPTS signal at the local base station under a particular condition, the UpPTS signal may be displaced directly into a time slot where a service data signal is arranged, and transmitted overlapping with the service data signal, and at this time the power of the service data signal in the same time slot as the UpPTS signal and hence the interfering power level of the service data signal to the UpPTS signal has to be limited in order to guarantee the performance of detecting the UpPTS signal.
The drawbacks in the prior art lie in a reduction in spectrum utilization of the system and a loss of the capacity of the system despite the additional guard interval or the limited power of the service data signal.